Successful weed management is essential for economical rice production. In rice production, propanil-based products are applied at various leaf stages of the weeds to prevent the growth of weeds. Propanil is a photosystem II inhibitor that controls broadleaf, grass, and sedge weeds. Propanil based products, such as Super Wham® (RiceCo, Inc., Memphis, Tenn.) have broad spectrum grass, broadleaf weed and sedge contact herbicidal activity, while at the same time being safe to rice. As a general rule of thumb, for every propanil susceptible grass leaf present, up to six leaves, one pound of propanil active ingredient per acre is needed to control the weed. Propanil resistant grasses are typically controlled by the addition of another grass herbicide to overcome resistance.
Another type of herbicides are the ACCase inhibitors such as: Cyhalofop sethoxydim, clethodim diclofop, fluazifop, fenoxaprop, quizalofop, clefoxydin and haloxyfop. ACCase inhibitor herbicides are known to be antagonistic when mixed with propanil (Kendig “New Rice Chemicals are Tools, Not Programs”, MO Delta Center, Rice Oct. 16, 2002). Poor weed control results have been observed with tank mixtures of ACCase inhibitor herbicides and propanil. G. Studebaker, University of Arkansas Pest Management News; (May 30, 2002); K. Smith. “Plan Ahead. Do a good job upfront and know your herbicide capacity,” Rice Journal (2004); C B Guy, “Profile: Clincher, Regiment herbicides (2003). (In Delta Farm Press.) In fact, for many ACCase inhibitor herbicides, use with a propanil based herbicide are restricted in the rate and recommendation charts distributed by the manufactures.